Stopper to prevent graft material slippage in a closed web stent-graft

ABSTRACT

A stent-graft has a closed web configuration in which end stent crowns or apexes do not extend beyond an end of a tubular graft. In order to permit interaction of the endmost crowns with tip capture fingers or prongs of a delivery system, the graft covers the endmost crowns but the endmost crowns are not coupled to the graft material and thus free to interact with the delivery system. In order to prevent slippage of the graft material at the endmost crowns and secure the longitudinal position of the graft material, one of a pair of stoppers is coupled on each of the opposing struts between which the unattached endmost crown is formed. In an embodiment, the stoppers are cylindrical tubes of a radiopaque material having a longitudinally-extending slit in a wall thereof.

BACKGROUND

1. Field of the Invention

The invention is related in general to implantable prostheses and inparticular to stent-grafts.

2. Related Art

Prostheses for implantation in blood vessels or other similar organs ofthe living body are, in general, well known in the medical art. Forexample, prosthetic vascular grafts constructed of biocompatiblematerials have been employed to replace or bypass damaged or occludednatural blood vessels. In general, endovascular grafts typically includea graft anchoring component that operates to hold a tubular graftcomponent of a suitable graft material in its intended position withinthe blood vessel. Most commonly, the graft anchoring component is one ormore radially compressible stents that are radially expanded in situ toanchor the tubular graft component to the wall of a blood vessel oranatomical conduit. Thus, endovascular grafts are typically held inplace by mechanical engagement and friction due to the opposition forcesprovided by the radially expandable stents.

Grafting procedures are also known for treating aneurysms. Aneurysmsresult from weak, thinned blood vessel walls that “balloon” or expanddue to aging, disease and/or blood pressure in the vessel. Consequently,aneurysmal vessels have a potential to rupture, causing internalbleeding and potentially life threatening conditions. Grafts are oftenused to isolate aneurysms or other blood vessel abnormalities fromnormal blood pressure, reducing pressure on the weakened vessel wall andreducing the chance of vessel rupture. As such, a tubular endovasculargraft may be placed within the aneurysmal blood vessel to create a newflow path and an artificial flow conduit through the aneurysm, therebyreducing if not nearly eliminating the exertion of blood pressure on theaneurysm.

In general, rather than performing an open surgical procedure to implanta bypass graft that may be traumatic and invasive, endovascular graftswhich may be referred to as stent-grafts are preferably deployed througha less invasive intraluminal delivery procedure. More particularly, alumen or vasculature is accessed percutaneously at a convenient and lesstraumatic entry point, and the stent-graft is routed through thevasculature to the site where the prosthesis is to be deployed.Intraluminal deployment is typically effected using a delivery catheterwith coaxial inner and outer tubes arranged for relative axial movement.For example, a self-expanding stent-graft may be compressed and disposedwithin the distal end of an outer catheter tube distal of a stop fixedto the inner member. The catheter is then maneuvered, typically routedthrough a body lumen until the end of the catheter and the stent-graftis positioned at the intended treatment site. The stop on the innermember is then held stationary while the outer tube of the deliverycatheter is withdrawn. The inner member prevents the stent-graft frombeing withdrawn with the sheath. As the sheath is withdrawn, thestent-graft is released from the confines of the sheath and radiallyself-expands so that at least a portion of it contacts and substantiallyconforms to a portion of the surrounding interior of the lumen, e.g.,the blood vessel wall or anatomical conduit.

In recent years to improve alignment during deployment of a stent-grafthaving self-expanding stents, various tip capture mechanisms have beenincorporated into the delivery system used for percutaneously deliveringthe prosthesis. For example, U.S. Patent Application Publication No.2006/0276872 to Arbefuielle et al. and U.S. Patent ApplicationPublication No. 2009/0276207 to Glynn et al., both herein incorporatedby reference in their entirety, describe tip capture mechanisms thatrestrain the proximal end stent of the stent-graft while the remainderof the stent-graft expands, then releases the proximal end stent. Theproximal end stent is attached to the graft material of the stent-graftso as to have an “open web” or “free flow” proximal end configuration inwhich the endmost crowns thereof extend past or beyond the graftmaterial such that the endmost crowns are exposed or bare, and thus freeto interact with a tip capture mechanism and couple the prosthesis tothe delivery system. The open web proximal end configuration allowsblood flow through the endmost crowns for perfusion during and/or afterimplantation. FIGS. 1A and 1B illustrate a delivery system 10 having atip capture mechanism 12 designed to couple or interact with astent-graft 14 having an open web or free flow proximal endconfiguration 16. More particularly, endmost crowns 18 engage or hookaround retractable finger or prong-like elements 20 of the tip capturemechanism. When an outer delivery shaft 22 is retracted to allowstent-graft 14 to self-expand, endmost crowns 18 of the end stent 15remain hooked around tip capture fingers 20, as shown in FIG. 1A. Torelease end stent 15, a shaft 24 coupled to finger or prong-likeelements 20 is retracted and end stent 15 is allowed to self-expand, asshown in FIG. 1B. The Captivia Delivery System manufactured by MedtronicVascular, Inc. of Santa Rosa, Calif. is one example of a delivery systemhaving a tip capture mechanism as described above, which may be used fordelivering endovascular stent-grafts such as the Valiant ThoracicStent-graft manufactured by Medtronic Vascular, Inc. of Santa Rosa,Calif.

Tip capture mechanisms have improved accuracy of deployment ofself-expanding stent-grafts having open web or free flow configurations.However, in some cases a closed web configuration may be required orchosen due to application and/or user preferences. In a closed webconfiguration, the endmost crowns do not extend past or beyond the graftmaterial but rather are covered by graft material. Embodiments hereofrelate to a stent-graft having a closed web configuration that mayinteract with a tip capture mechanism of a delivery system.

SUMMARY

Embodiments hereof relate to a prosthesis for implantation within a bodylumen. The prosthesis includes a tubular graft of a graft material and astent comprised of a plurality of crowns and a plurality of struts witheach crown being formed between a pair of opposing struts. The stent iscoupled to the graft material proximate to an end of the tubular graftso as to have a first set of crowns adjacent to the end of the tubulargraft and a second set of crowns distant from the end of the tubulargraft relative to the first set of crowns. A pair of stoppers is coupledadjacent to each crown of the first set of crowns, wherein each stopperhas a tubular configuration and is attached to a respective one of thepair of opposing struts that the crown is formed between. At least onestitch is made adjacent to each end of each stopper. The stiches securea longitudinal position of the graft material relative to each stopperand the strut it is attached to such that the first set of crowns arecovered by and free of direct attachment to the graft material of thetubular graft.

Embodiments hereof also relate to a prosthesis that includes a tubulargraft of a graft material and a stent coupled to the tubular graft andhaving endmost crowns that are inwardly spaced from an end of thetubular graft. Each endmost crown is a curved segment formed between apair of opposing struts. One or more of the endmost crowns are coveredby and free of direct attachment to the graft material of the tubulargraft. A pair of stoppers is coupled adjacent to each endmost crown thatis covered by and free of direct attachment to the graft material,wherein each stopper has a tubular configuration and is attached to arespective one of the pair of opposing struts that the crown is formedbetween. At least one stitch is made adjacent to each end of eachstopper, wherein the stiches abut against the ends of each stopper.

Embodiments hereof also relate to a prosthesis that includes a tubulargraft of a graft material and a stent coupled to the tubular graft andincluding a plurality of crowns and a plurality of struts with eachcrown being formed between a pair of opposing struts. The stent hasendmost crowns that are proximate to an end of the tubular graft, andone or more of the endmost crowns are covered by and free of directattachment to the graft material of the tubular graft. A pair ofstoppers is coupled adjacent to each endmost crown that is covered byand free of direct attachment to the graft material. Each stopper isattached to a respective one of the pair of opposing struts that thecrown is formed between. An outer diameter of each stopper is greaterthan an outer diameter of the stent struts such that each stopper endcreates a raised feature relative to the stent strut. At least onestitch is made adjacent to each end of each stopper, wherein the stichesabut against the respective raised feature created by each stopper.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of embodiments hereof asillustrated in the accompanying drawings. The accompanying drawings,which are incorporated herein and form a part of the specification,further serve to explain the principles of the invention and to enable aperson skilled in the pertinent art to make and use the invention. Thedrawings are not to scale.

FIGS. 1A and 1B are side views of a distal end of a delivery systemhaving a tip capture mechanism designed to couple or interact with astent-graft having an open web or free flow proximal end configuration.

FIG. 2 is a side view of a stent-graft having a closed web configurationwhich is configured to permit interaction with tip capture fingers of adelivery system, wherein endmost crowns of an end stent are not coupledto the graft material and include stoppers to prevent slippage of thegraft material according to an embodiment hereof.

FIG. 2A is an enlarged view of an endmost crown of FIG. 2, wherein theendmost crown is shown with stoppers but removed from the graft materialfor clarity purposes.

FIG. 3 is a perspective view of a stopper of FIG. 2, removed from thestent-graft for illustrative purposes, wherein the stopper is a slittube.

FIG. 4 and FIG. 5 are enlarged illustrations of an end stent crown ofFIG. 2 having a pair of stoppers coupled to the stent, wherein FIG. 4illustrates the inside surface of the graft material and FIG. 5illustrates the outside surface of the graft material.

FIG. 6 is a perspective view of a stopper according to anotherembodiment hereof, wherein the stopper is a tube.

FIG. 7 is a side view of a stent-graft having a stent configurationaccording to another embodiment hereof, wherein endmost crowns of thestent are not coupled to the graft material and include stoppers toprevent slippage of the graft material.

DETAILED DESCRIPTION

Specific embodiments of the present invention are now described withreference to the figures, wherein like reference numbers indicateidentical or functionally similar elements. Specific embodiments are nowdescribed with reference to the figures, wherein like reference numbersindicate identical or functionally similar elements. Unless otherwiseindicated, for the delivery system the terms “distal” and “proximal” areused in the following description with respect to a position ordirection relative to the treating clinician. “Distal” and “distally”are positions distant from or in a direction away from the clinician,and “proximal” and “proximally” are positions near or in a directiontoward the clinician. For the stent graft device proximal is the portionnearer the heart by way of blood flow path while distal is the portionof the stent graft further from the heart by way of blood flow path. Inaddition, the term “self-expanding”is used in the following descriptionwith reference to one or more stent structures of the prostheses hereofand is intended to convey that the structures are shaped or formed froma material that can be provided with a mechanical memory to return thestructure from a compressed or constricted delivery configuration to anexpanded deployed configuration. Non-exhaustive exemplary self-expandingmaterials include stainless steel, a pseudo-elastic metal such as anickel titanium alloy or nitinol, various polymers, or a so-called superalloy, which may have a base metal of nickel, cobalt, chromium, or othermetal. Mechanical memory may be imparted to a wire or stent structure bythermal treatment to achieve a spring temper in stainless steel, forexample, or to set a shape memory in a susceptible metal alloy, such asnitinol. Various polymers that can be made to have shape memorycharacteristics may also be suitable for use in embodiments hereof toinclude polymers such as polynorborene, trans-polyisoprene,styrene-butadiene, and polyurethane. As well poly L-D lactic copolymer,oligo caprylactone copolymer and poly cyclo-octine can be usedseparately or in conjunction with other shape memory polymers.

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Although the description of the invention is in the contextof treatment of blood vessels such as the coronary, carotid and renalarteries, the invention may also be used in any other body passagewayswhere it is deemed useful. Furthermore, there is no intention to bebound by any expressed or implied theory presented in the precedingtechnical field, background, brief summary or the following detaileddescription.

Embodiments hereof relate to a stent-graft having a closed webconfiguration, and more particularly relate to an apparatus and methodfor securing endmost crowns or apexes of a self-expanding stent to graftmaterial while still permitting interaction of the endmost crowns withtip capture fingers or prongs of a delivery system. As will be explainedin more detail below, the graft covers the endmost crowns of the stentbut the endmost crowns are not coupled to the graft material and thusare free to interact with the delivery system. Stoppers are coupled tothe stent adjacent to each unattached endmost crown in such a manner asto prevent slippage of the graft material at the endmost crowns and tosecure a longitudinal position of the graft material relative to thestent. Additional description and features are described below withreference to the figures.

Referring to FIG. 2, stent-graft prosthesis 200 includes a tubular graft210 having a first edge or end 202, a second edge or end 204, and a body203 there between which defines a lumen (not shown) through stent-graftprosthesis 200. In an embodiment, first end 202 of graft 210 may bereferred to as a proximal end of graft 210 and a proximal end ofstent-graft prosthesis 200, which is conventionally the end that iscoupled to a tip capture mechanism of a delivery system, and second end204 of graft 210 may be referred to as a distal end of graft 204 and adistal end of stent-graft prosthesis 200. Graft 210 may be formed fromany suitable graft material, for example and not limited to, alow-porosity woven or knit polyester, DACRON material, expandedpolytetrafluoroethylene, polyurethane, silicone, or other suitablematerials. In another embodiment, the graft material could also be anatural material such as pericardium or another membranous tissue suchas intestinal submucosa.

Stent-graft prosthesis 200 also includes at least oneradially-compressible stent or scaffold 206 that is coupled to graft 210for supporting the graft material and is operable to self-expand intoapposition with an interior wall of a body vessel (not shown). In theembodiment depicted in FIG. 1, stent-graft prosthesis 200 includes aseries of six independent or separate cylindrical stents 206. Each stent206 is constructed from a self-expanding or spring material, such asNitinol, and is a sinusoidal patterned ring including a plurality ofcrowns or bends 208 and a plurality of struts or straight segments 209with each crown being formed between a pair of opposing struts. Althoughshown with six stents, it will be understood by those of ordinary skillin the art that stent-graft prosthesis 200 may include a greater orsmaller number of sinusoidal patterned rings depending upon the desiredlength of stent-graft prosthesis 200 and/or the intended applicationthereof. For description purposes only, the stent that is coupledadjacent and proximate to first end 202 of graft 210 is referred toherein as first end stent 206A and the stent that is coupled adjacentand proximate to second end 204 of graft 210 is referred to herein assecond end stent 206B but it will be understood by those of ordinaryskill in the art that all of the stents may have identical or differentpatterns or configurations. Stents 206 are coupled to graft 210 bystitches 212 or other means known to those of skill in the art. In theembodiment shown in FIG. 2, stents 206 are coupled to an inside surfaceof graft 210. However, stents 206 may alternatively be coupled to anoutside surface of graft 210. When stent-graft 200 is used for treatingan aneurysm, stents 206 have sufficient radial spring force andflexibility to conformingly engage stent-graft prosthesis 200 with thebody lumen inner wall, to avoid excessive leakage, and preventpressurization of the aneurysm, i.e., to provide a leak-resistant seal.Although some leakage of blood or other body fluid may occur into theaneurysm isolated by stent-graft prosthesis 200, an optimal seal willreduce the chances of aneurysm pressurization and resulting rupture.

In another embodiment (not shown), rather than a series of independentor separate self-expanding stents/sinusoidal patterned rings, thesupport structure or scaffolding of stent-graft prosthesis 200 may haveother configurations such as a series of sinusoidal patterned ringscoupled to each other to form a self-expanding stent.

At least first end 202 of stent-graft prosthesis 200 has a closed webconfiguration in which the endmost crowns 208 of end stent 206A arecovered or lined by graft 210 and do not extend past or beyond first end202 of graft 210. As used herein, “endmost” crowns are the crowns orpeaks of a stent that are most proximate to and inwardly spaced apartfrom an end or edge of graft 210, such as first end or edge 202. In theembodiment of FIG. 2, end stents 206A is coupled to the graft materialso as to have a first or endmost set of crowns 208 adjacent to the firstend 202 of graft 210 and a second or opposing set of crowns 211 distantfrom first end 202 of graft 210 relative to the endmost set of crowns.Endmost crowns 208 of first end stent 206A are not coupled or stitchedto graft 210 and are free from direct attachment to graft 210, so thatthe endmost crowns 208 may interact with a tip capture mechanism on adelivery system as previously described herein in relation to FIG. 1Aand FIG. 1B. In the embodiment depicted in FIG. 2, the endmost crowns208B of end stent 206B are also covered or lined by graft 210 and do notextend outside of or beyond the end of graft 210. However, in theembodiment of FIG. 2, the endmost crowns 208B of second end stent 206Bare stitched or otherwise secured to graft 210 because such crowns arenot used for coupling the prosthesis to the delivery system. In anotherembodiment (not shown), the endmost crowns 208B of second stent 206B arenot coupled or stitched to graft 210 and are free from direct attachmentto graft 210 so as to be accessible for attachment to the deliverysystem. In yet another embodiment (not shown), the endmost crowns 208Bof second end stent 206B may extend beyond second end 204 of graft 210in an open web or free-flow configuration.

A pair of stoppers 214 are coupled to first end stent 206A proximate oradjacent to each unattached endmost crown 208 such that there is astopper adjacent to opposing sides 230, 232 of the endmost crown asshown in FIG. 2 and FIG. 2A. FIG. 2A illustrates an endmost crown 208having stoppers 214 but the graft material is not shown for claritypurposes. Each endmost crown 208 is a curved segment formed between apair of opposing struts 209 as described above, and a first stopper 214is coupled to the strut adjacent to a first side 230 of each unattachedendmost crown 208 and a second stopper 214 is coupled to the opposing orsecond strut adjacent to an opposing or second side 232 of eachunattached endmost crown 208. “Opposing side” of an endmost crown asused herein refers a point or location on the stent wire or wire-likestructure that forms the stent where the crown transitions to the strut,i.e., where the curved segment transitions to the straight segment. Thelocation of each stopper on each strut may vary according toapplication, but each stopper is at least spaced apart from the peak orapex of each endmost crown 208 so that the endmost crowns 208 may beused to couple prosthesis 200 to a delivery system having a tip capturemechanism.

Referring to FIG. 3, in one embodiment hereof, each stopper 214 has atubular configuration and includes a cylindrical body 320 defining alumen 324 there through. Cylindrical body 320 includes an outer diameterD_(O) and an inner diameter D_(I). Inner diameter D_(I) is equal to orslightly greater than an outer diameter of stent strut 209 such thatstopper 214 may be fitted there over. Outer diameter D_(O) is greaterthan inner diameter D_(I) and accordingly is greater than the outerdiameter of stent strut 209.

Cylindrical body 320 includes a slit or slot 322 extending through thewall thereof and extending the entire length thereof, i.e., has aslit-tube configuration, which allows each stopper 214 to be placed orclipped directly onto a stent, for instance first end stent 206A. Duringassembly or manufacture of stent-graft prosthesis 200, stoppers 214 arefirst positioned on first end stent 206A such that there is a stopper onopposing struts of each unattached endmost crown 208. After beingproperly positioned, each stopper 214 is crimped and bonded onto stentstrut 209. Graft 210 is then secured to first end stent 206A adjacentfirst and second ends 416, 418, respectively, of each stopper 214.Adjacent to second end 418 of stopper 214, graft 210 is secured to firstend stent 206A with at least one stitch or suture 228 (see FIG. 2 andFIGS. 4-5). Adjacent to first end 416 of stopper 214, graft 210 issecured to first end stent 206A with at least one stitch 226 (see FIG. 2and FIGS. 4-5). In an embodiment, stitch 226 is a double stitch 226,which is stronger than a single stitch, and is positioned adjacent tofirst end 416 of stopper 214 to ensure that graft 210 is secure againsteach stopper 214. In another embodiment (not shown), stitch 226 may be atriple stitch to secure graft 210 to first end stent 206A adjacent tothe first end 416 of each stopper 214.

Stitches 226, 228 secure the longitudinal position of the graft materialof graft 210 with respect to stopper 214 and strut 209 to which stopper214 is attached, and accordingly stopper 214 together with stitches 226,228 prevent the graft material of graft 210 from undesirable shifting orslipping during operation. More particularly, stitches 226, 228 abutagainst end faces of first and second ends 416, 418, respectively, ofstopper 214 and are not permitted to pass or slip over the stopper sincestopper 214 has outer diameter D_(O) which is greater than the outerdiameter of stent strut 209. Since the outer diameter D_(O) of eachstopper is greater than an outer diameter of struts 209, end faces 317,319 of stopper ends 416, 418, respectively, create a raised featurealong or relative to the surface of strut 209 against which stitches226, 228 may bear during loading and/or deployment procedures concerningstent-graft prosthesis 200, and thereby prevent shifting or slippage ofgraft material relative to stopper 214. Without a stopper in place andendmost crowns 208 unattached to graft 210, the graft material coveringor lining the endmost crowns may slip or move and cause undesiredbunching and/or wrinkling of graft 210 during loading and/or deploymentprocedures. If the graft material slips, bunches, or wrinkles, the graftmaterial may become misaligned and endmost crowns 208 may be undesirablyexposed after deployment of stent-graft prosthesis 200. However,stoppers 214 ensure that graft 210 does not slip distally or downwardsat endmost crowns 208 but rather remains covering the endmost crowns208.

In an embodiment, stoppers 214 are made of a radiopaque material such asbut are not limited to tungsten, tantalum, platinum, platinum andiridium alloy, rhenium, gold, molybdenum, silver, and alloys containingone or more thereof. When formed of a radiopaque material, stoppers 214advantageously operate as radiopaque markers to track the position offirst end stent 206A within the body. In another embodiment, stoppers214 may be formed from stainless steel or other suitable material.

FIG. 6 illustrates another configuration of a stopper which operates toprevent a graft from undesirable shifting or slipping away fromunattached endmost crowns. Similar to stopper 214, stopper 614 has atubular configuration and includes a cylindrical body 620 defining alumen 624 there through. However, cylindrical body 620 does not includea slit or slot extending through the wall thereof. During manufacture,prior to formation of end stent 206A into a ring, a stopper 614 ispositioned on the wire that is to form end stent 206A such that there isa stopper on opposing struts of each crown that is to form an unattachedendmost crown of the finished stent. After being properly positioned,each stopper 614 is crimped and bonded onto the stent wire and the stentwire is formed into a ring, i.e., the ends of the sinusoidal wire arecrimped together. Graft material may then be secured to the end stent asdescribed above with respect to stopper 214.

FIG. 7 illustrates a stent-graft prosthesis 700 according to anotherembodiment hereof in which the prosthesis includes a tubularradially-compressible stent or scaffold 706 rather than a plurality ofstents formed as independent sinusoidal patterned rings. Stent 706 iscoupled within a tubular graft 710 to extend from a first end 702 to asecond end 704 thereof for supporting the graft material and is operableto self-expand into apposition with an interior wall of a body vessel(not shown). In the embodiment depicted in FIG. 7, stent 706 is aunitary tubular component having diamond-shaped openings 734, which maybe formed by various conventional stent forming methods as would beunderstood by one of ordinary skill in the art. Stent 706 includesendmost crowns 708 that are proximate to and inwardly spaced from anedge or end 702 of graft 710. Each endmost crown 708 is a curved segmentextending between opposing struts 709 on stent 706. Stoppers 714, whichare similar to stoppers 214 described above, are coupled onto each strut709 adjacent to opposing sides 730, 732 of each endmost. The location ofeach stopper on each strut may vary according to application, but asdescribed above with respect to stoppers 714, the distance between thepeak or apex of each endmost crown 708 and stopper 714 is sufficient toutilize the endmost crowns to couple prosthesis 700 to a delivery systemhaving a tip capture mechanism. Similar to stopper 214, at least onestitch is made adjacent to each end of each stopper 714 in order tocouple graft material of graft 710 to stent 706, although such stitchesare not shown in FIG. 7 for sake of clarity.

While various embodiments according to the present invention have beendescribed above, it should be understood that they have been presentedby way of illustration and example only, and not limitation. Forexample, although the stoppers are illustrated on the first or proximalend of the tubular graft which is conventionally coupled to a tipcapture mechanism of a delivery system, it would be understood by one ofordinary skill in the art that the stoppers and respective stitches mayalso or alternatively be coupled adjacent to endmost crowns of a stentproximate the second or distal end of the tubular graft depending on thedelivery system used to deliver the stent-graft. It will be apparent topersons skilled in the relevant art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the invention. Thus, the breadth and scope of the present inventionshould not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the appendedclaims and their equivalents. It will also be understood that eachfeature of each embodiment discussed herein, and of each reference citedherein, can be used in combination with the features of any otherembodiment. All patents and publications discussed herein areincorporated by reference herein in their entirety.

What is claimed is:
 1. A prosthesis for implantation within a bodylumen, the prosthesis comprising: a tubular graft of a graft material; astent comprised of a plurality of crowns and a plurality of struts witheach crown being formed between a pair of opposing struts, the stentbeing coupled to the graft material proximate to an end of the tubulargraft so as to have a first set of crowns adjacent to the end of thetubular graft and a second set of crowns distant from the end of thetubular graft relative to the first set of crowns; a pair of stopperscoupled adjacent to each crown of the first set of crowns, wherein eachstopper has a tubular configuration and is attached to a respective oneof the pair of opposing struts that the crown is formed between; and atleast one stitch made adjacent to each end of each stopper, wherein thestiches secure a longitudinal position of the graft material relative toeach stopper and the strut it is attached to such that the first set ofcrowns are covered by and free of direct attachment to the graftmaterial of the tubular graft.
 2. The prosthesis of claim 1, whereineach stopper is a cylindrical body defining a lumen there through. 3.The prosthesis of claim 2, wherein the cylindrical body includes a slitthrough the wall of the cylindrical body that extends the entire lengthof the cylindrical body.
 4. The prosthesis of claim 1, wherein the graftis secured to the stent with a single stitch adjacent to a first end ofeach stopper and wherein the graft is secured to the stent with at leasta double stitch adjacent to a second end of each stopper, the second endof each stopper being closer to the crown than the first end of eachstopper.
 5. The prosthesis of claim 1, wherein each stopper is formed ofa radiopaque material.
 6. The prosthesis of claim 1, further comprising:a plurality of stents coupled to a body of the tubular graft, whereineach stent is a sinusoidal patterned ring formed from a self-expandingmaterial.
 7. The prosthesis of claim 1, wherein the stent is coupled toan inside surface of the graft.
 8. A prosthesis for implantation withina body lumen, the prosthesis comprising: a tubular graft of a graftmaterial; a stent coupled to the tubular graft and having endmost crownsthat are inwardly spaced from a first end of the tubular graft, eachendmost crown being a curved segment formed between a pair of opposingstruts, wherein one or more of the endmost crowns are covered by andfree of direct attachment to the graft material of the tubular graft; apair of stoppers coupled adjacent to each endmost crown that is coveredby and free of direct attachment to the graft material, wherein eachstopper has a tubular configuration and is attached to a respective oneof the pair of opposing struts that the crown is formed between; and atleast one stitch made adjacent to each end of each stopper, wherein thestiches abut against an end face of each stopper.
 9. The prosthesis ofclaim 8, wherein each stopper is a cylindrical body defining a lumenthere through.
 10. The prosthesis of claim 9, wherein the cylindricalbody includes a slit through the wall of the cylindrical body thatextends the entire length of the cylindrical body.
 11. The prosthesis ofclaim 8, wherein the graft is secured to the stent with a single stitchadjacent to a first end of each stopper and wherein the graft is securedto the stent with at least a double stitch adjacent to a second end ofeach stopper, the second end of each stopper being closer to the endmostcrown than the first end of each stopper.
 12. The prosthesis of claim 8,wherein each stopper is formed of a radiopaque material.
 13. Theprosthesis of claim 8, wherein the stent is coupled to the tubular graftto extend from the first end of the graft to a second end of the tubulargraft.
 14. The prosthesis of claim 8, further comprising: a plurality ofstents coupled to a body of the tubular graft, wherein each stent is asinusoidal patterned ring formed from a self-expanding material.
 15. Aprosthesis for implantation within a body lumen, the prosthesiscomprising: a tubular graft of a graft material; a stent coupled to thetubular graft and including a plurality of crowns and a plurality ofstruts with each crown being formed between a pair of opposing struts,the stent having endmost crowns that are proximate to an end of thetubular graft, wherein one or more of the endmost crowns are covered byand free of direct attachment to the graft material of the tubulargraft; a pair of stoppers coupled adjacent to each endmost crown that iscovered by and unattached to the graft material, wherein each stopper isattached to a respective one of the pair of opposing struts that thecrown is formed between and an outer diameter of each stopper is greaterthan an outer diameter of the struts such that each stopper end is araised feature relative to the respective strut; and at least one stitchmade adjacent to each end of each stopper, wherein the stiches abutagainst the respective raised feature of each stopper end.
 16. Theprosthesis of claim 15, wherein each stopper is a cylindrical bodydefining a lumen there through and the raised feature is an end surfacethereof.
 17. The prosthesis of claim 16, wherein the cylindrical bodyincludes a slit through the wall of the cylindrical body that extendsthe entire length of the cylindrical body.
 18. The prosthesis of claim15, wherein the graft is secured to the stent with a single stitchadjacent to a first end of each stopper and wherein the graft is securedto the stent with at least a double stitch adjacent to a second end ofeach stopper, the second end of each stopper being closer to the crownthan the first end of each stopper.
 19. The prosthesis of claim 15,wherein each stopper is formed of a radiopaque material.
 20. Theprosthesis of claim 15, further comprising: a plurality of stentscoupled to a body of the tubular graft, wherein each stent is asinusoidal patterned ring formed from a self-expanding material.